Microtubule-damaging agents enhance RASSF1A-induced cell death in lung cancer cell lines

Molecular profile of nasopharyngeal carcinoma: analysing tumour suppressor gene promoter hypermethylation by multiplex ligation-dependent probe amplification

Aims

To assess differences in methylation profiles, and thus pathogenesis, between Epstein-Barr virus (EBV)-positive and negative nasopharyngeal carcinomas (NPCs). Also, promoter hypermethylation is a common phenomenon in early carcinogenesis to inactivate tumour suppressor genes. Since epigenetic changes are reversible, the therapeutic application of methylation inhibitors could provide treatment options.

Methods

We evaluated promoter hypermethylation profiles of 22 common tumour suppressor genes in 108 NPCs using methylation-specific multiplex ligation-dependent probe amplification. Correlation between methylation, clinicopathological features (including EBV) and survival was examined. Cluster analysis was also performed.

Results

Hypermethylation of RASSF1A and ESR1 was significantly more frequent in EBV-positive NPC, while hypermethylation of DAPK1 was more frequent in EBV-negative NPC. In logistic regression, age, with EBV-positive NPC occurring at earlier age, and RASSF1, with RASSF1 hypermethylation being more frequent in EBV-positive NPC, remained significant. In EBV-positive NPC, hypermethylation of RASSF1A predicted worse overall survival (OS) (HR 3.058,95% CI 1.027 to 9.107). In EBV-negative NPC, hypermethylated adenomatous polyposis coli (APC) was a predictor of poor disease-free survival (DFS) (HR 6.868, 95% CI 2.142 to 22.022).

Conclusion

There are important epigenetic differences between EBV-negative and EBV-positive NPCs, with EBV-negative NPC having a more similar hypermethylation profile to other head and neck squamous cell carcinomas than EBV-positive NPC. Hypermethylation of RASSF1A might contribute to worse OS in EBV-positive NPC, and may be an important event in the pathogenesis of EBV-infected NPC. Hypermethylation of APC might contribute to worse DFS in EBV-negative NPC.

KIBRA attains oncogenic activity by repressing RASSF1A

BACKGROUND

KIBRA-initially identified as a neuronal associated protein is now shown to be functionally associated with other tissue types as well. KIBRA interacts with dyenin light chain 1 and this interaction is essential for oestrogen receptor transactivation in breast cancer cells. KIBRA as a substrate of Cdk1, Aurora kinase and ERK plays an important role in regulating cell cycle, cell proliferation and migration. Despite these evidences, the exact role of KIBRA in cancer progression is not known.

METHODS

We studied the expression of KIBRA in breast tissues and breast cancer cell lines by western blotting, immunohistochemisry (IHC) and RT-PCR. Stable over expression and knockdown clones were generated to study the transforming properties of KIBRA by conventional assays. Xenograft studies were performed in nude mice to study the in vivo tumourigenic efficacy of KIBRA. qPCR array was performed to understand the molecular mechanism behind oncogenic activity of KIBRA.

RESULTS

Our results showed that KIBRA is upregulated in breast cancer cells and in malignant human breast tumours by both western blotting and IHC. Interestingly, we found that KIBRA expression level goes up with increase in breast cancer progression in well-established MCF10A model system. Further, results from stable overexpression clones of KIBRA in fibroblasts (Rat-1) and epithelial breast cancer cells (ZR75) and lentiviral short hairpin RNA-mediated knockdown (KD) clones of KIBRA in ZR75 showed increase in transforming properties with KIBRA overexpression and vice-versa. Results also showed that fibroblasts stably overexpressing KIBRA showed increased tumourigenic potential in nude mice. By adopting a quantitative PCR array-based approach, we identified RASSF1A, a tumour suppressor, as a transcriptional target of KIBRA.

CONCLUSIONS

This is the first study to demonstrate the in vivo tumourigenic property of KIBRA in a nude mouse model and also unravel the underlying molecular mechanism of KIBRA-mediated transformation via repression of RASSF1A.British Journal of Cancer advance online publication, 29 June 2017; doi:10.1038/bjc.2017.192 www.bjcancer.com.

RASSF1A and SIRT6 in non-small cell lung cancer: Relationship with clinical outcome

This study investigated the expression of RASSF1A and SIRT6 in non-small cell lung cancer (NSCLC) and its relationship with clinical prognosis. The expression in 122 cases of NSCLC tissues (NSCLC group) and 122 cases of normal lung tissues (NOR group) during the same period were detected by immunohistochemical Super Pic Ture™ Polymer two-step method, and the relationship between its expression and the clinicopathological features and prognosis of patients was analyzed. The positive expression rates of RASSF1A and SIRT6 in NSCLC group were lower than those in the normal group (55.74 vs. 84.43% and 52.46 vs. 82.49%, P<0.01). The differences in expression intensity of RASSF1A in NSCLC tissues between different tumor pathological types, tumor differentiation degrees and lymph node metastases were statistically significant, and the differences in expression intensity of SIRT6 between different TNM stages, tumor differentiation degrees and lymph node metastases were statistically significant. There was a positive correlation between the expression of RASSF1A and SIRT6 in NSCLC group (r=0.532, P<0.01). The 3-year survival rate of patients with high-expression of RASSF1A was higher than in those with low-expression of RASSF1A (81.33 vs. 39.45%, log-rank χ²=19,102, P<0.01); the 3-year survival rate of patients with high-expression of SIRT6 was higher than in those with low-expression of SIRT6 (83.51 vs. 42.43%, log-rank χ²=17,180, P<0.01). The low expression of RASSF1A and SIRT6 and lymph node metastasis were the risk factors affecting the prognosis of NSCLC patients. There is a better correlation between the expression of RASSF1A and SIRT6 in NSCLC tissues, and the detection of their expression is of great significance in the judgement of clinicopathological features and prognosis of NSCLC patients.

RASSF1A and ERCC1 expression levels might be predictive of prognosis in advanced, recurrent, and metastatic squamous cell carcinoma of the head and neck treated with docetaxel and cisplatin

BACKGROUND

The purpose of this study was to test the hypothesis that the immunohistochemical expression of ERCC1 and RASSF1A would predict both response to and survival after docetaxel and cisplatin combination chemotherapy in inoperable or recurrent head and neck squamous cell carcinoma.

PATIENTS AND METHODS

A total of 54 patients were treated with frontline systemic chemotherapy composed of docetaxel (60 mg/m(2)) and cisplatin (65 mg/m(2)), every 3 weeks for up to 6 cycles. The expression levels of ERCC1 and RASSF1A were evaluated in the available 36 prechemotherapy samples.

RESULTS

The overall objective response rate was 35% (complete remission 12% and partial remission 23%). The median progression-free survival and overall survival (OS) times were 5.0 months (95% confidence interval (CI), 3.7-6.4 months) and 24.2 months (95% CI, 3.5-45.0 months), respectively. The status of low ERCC1 and high RASSF1A expression was an independent favorable prognostic factor for OS in multivariate analysis (p = 0.043; hazard ratio, 7.224; 95% CI, 1.060-49.217). Toxicities were comparable with those of previously reported trials.

CONCLUSIONS

Less intensive doses of cisplatin and docetaxel are active but not effective in reducing toxicity. Also, both ERCC1 and RASSF1A might be useful prognostic markers in this regimen.

Promoter methylation of RASSF1A modulates the effect of the microtubule-targeting agent docetaxel in breast cancer

Docetaxel is one of the most commonly used chemotherapeutic agents in breast cancer. To avert from significant toxicities with no clinical benefit, identification of predictive markers for response is one of the most important unsolved clinical needs. Therefore, the potential associations of RASSF1A hypermethylation and response to docetaxel-based chemotherapy were evaluated, and the underlying mechanism was studied. The expression of RASSF1A in breast cancer cell lines and tissues of normal breast, ductal carcinoma in situ (DCIS), and breast cancer (n=45) was analyzed by immunohistochemistry and western blot analysis. Immunohistochemical staining showed that the expression of RASSF1A was frequently lost in primary breast cancers and human breast cancer cell lines, while normal breast tissues or DCIS displayed moderate to strong expression. Furthermore, quantitative methylation analysis of the RASSF1A promoter region in 45 primary breast cancers revealed that RASSF1A was frequently methylated in primary breast cancers (≥20% methylation in 53% of the patients), and prospective analysis in patients with locally advanced or recurrent breast cancer showed that the mean level of methylation of RASSF1A was significantly higher in patients who did not respond to docetaxel-based chemotherapy (30.6±8.5%) than patients with partial or complete response (20.1±11.2%, p=0.042). Finally, in vitro studies showed that RASSF1A had cooperative activity in suppression of cancer cell growth and proliferation by enhancing docetaxel-induced cell cycle arrest. Our results suggest that hypermethylated RASSF1A is an important modulating factor for the efficacy of docetaxel-based chemotherapy in breast cancer.

Role of cyclin B1/Cdc2 up-regulation in the development of mitotic prometaphase arrest in human breast cancer cells treated with nocodazole

BACKGROUND

During a normal cell cycle, the transition from G₂ phase to mitotic phase is triggered by the activation of the cyclin B1-dependent Cdc2 kinase. Here we report our finding that treatment of MCF-7 human breast cancer cells with nocodazole, a prototypic microtubule inhibitor, results in strong up-regulation of cyclin B1 and Cdc2 levels, and their increases are required for the development of mitotic prometaphase arrest and characteristic phenotypes.

METHODOLOGY/PRINCIPAL FINDINGS

It was observed that there was a time-dependent early increase in cyclin B1 and Cdc2 protein levels (peaking between 12 and 24 h post treatment), and their levels started to decline after the initial increase. This early up-regulation of cyclin B1 and Cdc2 closely matched in timing the nocodazole-induced mitotic prometaphase arrest. Selective knockdown of cyclin B1or Cdc2 each abrogated nocodazole-induced accumulation of prometaphase cells. The nocodazole-induced prometaphase arrest was also abrogated by pre-treatment of cells with roscovitine, an inhibitor of cyclin-dependent kinases, or with cycloheximide, a protein synthesis inhibitor that was found to suppress cyclin B1 and Cdc2 up-regulation. In addition, we found that MAD2 knockdown abrogated nocodazole-induced accumulation of cyclin B1 and Cdc2 proteins, which was accompanied by an attenuation of nocodazole-induced prometaphase arrest.

CONCLUSIONS/SIGNIFICANCE

These observations demonstrate that the strong early up-regulation of cyclin B1 and Cdc2 contributes critically to the rapid and selective accumulation of prometaphase-arrested cells, a phenomenon associated with exposure to microtubule inhibitors.

(-)-Anonaine induces DNA damage and inhibits growth and migration of human lung carcinoma h1299 cells

The anticancer effects of (-)-anonaine were investigated in this current study. (-)-Anonaine at concentration ranges of 50-200 μM exhibited significant inhibition to cell growth and migration activities on human lung cancer H1299 cells at 24 h, albeit cell cycle analyses showed that (-)-anonaine at the above concentration ranges did not cause any significant changes in cell-cycle distributions. Significant nuclear damages of H1299 cells were observed with 10-200 μM (-)-anonaine treatment in a comet assay, whereas higher concentrations (6 and 30 mM) of (-)-anonaine concentrations were required to cause DNA damages in an in vitro plasmid cleavage assay. In summary, our results demonstrated that (-)-anonaine exhibited dose-dependent antiproliferatory, antimigratory, and DNA-damaging effects on H1299 cells. We inferred that (-)-anonaine can cause cell-cycle arrest and DNA damage to hamper the physiological behavior of cancer cells at 72 h, and therefore, it can be useful as one of the potential herbal supplements for chemoprevention of human lung cancer.

[Prognostic value of methylation status of RASSF1A gene as an independent factor of non-small cell lung cancer]

背景与目的

研究发现在很多肿瘤中都存在RASSF1A基因启动子区域高甲基化状态导致基因表达失活的现象，本研究就RASSF1A基因启动子的甲基化状态与非小细胞肺癌预后的关系进行探讨。

方法

采用甲基化特异的PCR检测150例非小细胞肺癌和20例肺部良性病变RASSF1A启动子甲基化状态。

结果

150例非小细胞肺癌中58例发现RASSF1A启动子存在甲基化（58/158, 38.7%），20例肺部良性病变中无一例发现RASSF1A启动子甲基化。存在RASSF1A启动子高甲基化的病例预后较未发现RASSF1A甲基化的病例差（P=0.004），Cox回归分析显示RASSF1A启动子的甲基化状态是非小细胞肺癌术后的一个预后相关因素（RR=1.584, 95%CI: 1.040-2.411, P=0.032）。

结论

MSP法检测RASSF1A启动子甲基化状态可以作为非小细胞肺癌术后的一个预后评价指标。

Alpha-santalol, a chemopreventive agent against skin cancer, causes G2/M cell cycle arrest in both p53-mutated human epidermoid carcinoma A431 cells and p53 wild-type human melanoma UACC-62 cells

Background

α-Santalol, an active component of sandalwood oil, has shown chemopreventive effects on skin cancer in different murine models. However, effects of α-santalol on cell cycle have not been studied. Thus, the objective of this study was to investigate effects of α-santalol on cell cycle progression in both p53 mutated human epidermoid carcinoma A431 cells and p53 wild-type human melanoma UACC-62 cells to elucidate the mechanism(s) of action.

Methods

MTT assay was used to determine cell viability in A431 cells and UACC-62; fluorescence-activated cell sorting (FACS) analysis of propidium iodide staining was used for determining cell cycle distribution in A431 cells and UACC-62 cells; immunoblotting was used for determining the expression of various proteins and protein complexes involved in the cell cycle progression; siRNA were used to knockdown of p21 or p53 in A431 and UACC-62 cells and immunofluorescence microscopy was used to investigate microtubules in UACC-62 cells.

Results

α-Santalol at 50-100 μM decreased cell viability from 24 h treatment and α-santalol at 50 μM-75 μM induced G₂/M phase cell cycle arrest from 6 h treatment in both A431 and UACC-62 cells. α-Santalol altered expressions of cell cycle proteins such as cyclin A, cyclin B1, Cdc2, Cdc25c, p-Cdc25c and Cdk2. All of these proteins are critical for G₂/M transition. α-Santalol treatment up-regulated the expression of p21 and suppressed expressions of mutated p53 in A431 cells; whereas, α-santalol treatment increased expressions of wild-type p53 in UACC-62 cells. Knockdown of p21 in A431 cells, knockdown of p21 and p53 in UACC-62 cells did not affect cell cycle arrest caused by α-santalol. Furthermore, α-santalol caused depolymerization of microtubules similar to vinblastine in UACC-62 cells.

Conclusions

This study for the first time identifies effects of α-santalol in G₂/M phase arrest and describes detailed mechanisms of G₂/M phase arrest by this agent, which might be contributing to its overall cancer preventive efficacy in various mouse skin cancer models.